Cognitive impairment after surgery occurs frequently in the large number of increasingly elderly patients undergoing cardiac surgery every year. Postoperative cognitive deficit (POCD) is present in 36-50% of patients in the early phases after surgery and has been shown to adversely impact quality of life as much as one year after surgery. The objective of our multidisciplinary Neurological Outcome Research Group is to understand the mechanisms underlying neurologic and neurocognitive dysfunction after cardiac surgery and to reduce the incidence of these devastating outcomes. Despite substantial advancement in technology, pharmacology, and perioperative organ protection leading to reductions in mortality associated with cardiac surgery, the incidence of POCD has changed little over the last ten years. While multiple etiologic factors have been proposed for this neurological injury including cerebral embolic processes and hypoperfusion, the role of brain amyloid burden has never been examined. Because cardiac surgery generally takes place in the aged, it is possible that the cognitive dysfunction seen in surgical patients is a form of mild cognitive impairment (MCI), a condition characterized by accumulation of amyloid beta-fibrils. Thus the primary aim of our study is to determine the relationship between b-amyloid deposition and POCD using positron emission tomography (PET) and a newer PET tracer with a high affinity for b-amyloid fibrils. Secondarily, we will assess regional patterns of amyloid deposition in patients with POCD and compare these patterns with a previously imaged group of 40 MCI subjects and 40 elderly controls. Little is more devastating to a patient or the patient's family than to have a successful operation that prolongs life, but is complicated by cognitive impairment resulting in a diminished quality of life and loss of functional independence. The results of our study will be invaluable to the prevention of POCD in that we will define the role of regional amyloid burden in POCD using functional imaging markers that reveal the earliest neuronal changes and thus generate new mechanistic insights.